This invention relates to a steering mechanism which requires a reduced amount of steering wheel operation to steer the steered wheels up to their maximum steering angle.
Steering mechanisms commonly used in automobiles require more than one full turn of the steering wheel to achieve steering of the steered wheels up to their maximum steering angle. Such steering wheel operation constitutes a fatigue factor.
Therefore, a fast reaction steering mechanism which enables a large steering angle of the steered wheels by a small operation of the steering wheel has been in demand.
To meet such a requirement, the steering gear ratio can be set at a high value, as used in formula cars. However, if the gear ratio is increased, then, steering response in the vicinity of the central position of the steering wheel becomes oversensitive, and, a high speed corrective steering becomes difficult.
In such a fast reaction steering mechanism, since a large change in angle is produced in the steering wheels from a small change in steering angle of the steering wheel, it is preferable that the steering force be increased as the steering angle increases. In this manner, the steering angle is not abruptly increased even if the mechanism is carelessly operated by a driver who is accustomed to an ordinary steering system.
However, if a fast reaction is to be achieved simply by increasing the steering gear ratio, since the steering force is almost constant with respect to changes in steering angle, it is liable to cause excessively sharp steering, which constitutes a safety problem. If the steering force is set high to prevent such sharp steering, the steering force in the vicinity of the central position of the steering wheel also increases, which tends to increase the driver's fatigue.